Agricultural water-land optimization for multiple cropping under crop growth stages and farmer budget constraints

CONTEXT Optimizing water and land resources for multiple cropping face three major challenges: temporal mismatches, periodic land overload, and disconnects from farmers' budget constraints. OBJECTIVE This study proposes a tiered framework that synchronizes crop-stage water needs, monthly supply, land limits, and budget ceilings to generate feasible, differentiated allocation plans. METHOD The year was divided into 35 sub-periods based on crop growth-stage transitions, with two-way mapping among stages, sub-periods, and months to resolve mismatches. Binary planting variables capture crop distribution and generate time-series area constraints. A dual-path budget grading framework is embedded in the multi-objective model to account for data availability. Where survey data exist, per-area budget is the clustering indicator; Ward's clustering method and silhouette coefficient determine K. Otherwise, standardized budget scenarios are constructed using minimum feasible cost and land-use potential. The model is solved by NSGA-II, and incremental benefit-cost ratio analysis guides tiered recommendations. RESULTS AND CONCLUSIONS Applied to Gaozhou Irrigation District, the method achieved water satisfaction 91.75%–100% across growth stages. Net benefit increased 6.4% from 96,426.51 CNY (13,393 USD) to 102,587.59 CNY (14,248 USD), and water deficit reduced 29.7% to 753 m 3 . With budget ceilings 25,700, 44,300, 65,600 CNY, rice area expands without per-unit irrigation change; peanut area and per-unit irrigation rise only at low-medium transition; further increments drive area expansion but raise water deficit. The incremental benefit-cost ratio values are 1.30 and 1.53 CNY/CNY for low-to-medium and medium-to-high transitions, respectively. SIGNIFICANCE By converting theoretical optima into budget-differentiated feasible strategies, the framework supports precision irrigation scheduling and provides a practical basis for designing targeted agricultural subsidies and water-saving policies.